Brazing flux



United States Patent 3,175,933 BRAZING FLUX Rene D. Wasserman, Stamford, and Daniel D. Zielik,

Fair-field, C0nn., assignors to Eutectic Welding Alloys gorporation, Flushing, N.Y., a corporation of New ork No Drawing. Filed May 1, 1962, Ser. No. 191,427 4 Claims. (Cl. 148-26) This invention relates to a flux for depositing brass alloys upon parent metals, and it more particularly relates to such a flux for use in conjunction with cast iron parent materials.

The graphite that is always present in cast iron and the grease, oil, rust and other dirt that usually accumulate upon it make it diflicult for brass alloys to be secured to it by conventional brazing or welding techniques. These brass alloys also fume excessively when subjected to depositing heat thereby discharging clouds of obnoxious zinc vapors thereby endangering the health of their appliers.

An object of this invention is to provide a flux which aids the wetting of parent materials, particularly cast iron, by brass alloys; and

Another object is to provide such a flux which suppresses the fuming of brass alloys when heat is applied to them.

In accordance with this invention a brazing flux is compounded from the following constituents in the indicated ranges of percentages by weight.

Constituent Range Example Boron oxide and its compounds, particularly alkali metal borates 35-82. 7 60 Active metal fluorides 6-33 14. Chloride salts of active metals 8-32 17 Silicon-containing dcoxidizers 0. 5-4 1. 5 Alkali metal hydroxide 0.5-7.5 1. 5

Mixture of nickel or molybdenum oxide and fluoride including at least 10% of either oxide or fluoride 0. 3-14 1 Alkali metal silicate, particularly sodium silicate" l-10 2. 5 Calcium oxide 1-8 2 This flux can be used as a separate medium in paste or powder form, or it can be spread, painted or extruded about the brass core wire.

A particularly effective example of this type of flux incorporates the following constituents in the indicated percentages by weight.

Approximately equal mixture of nickel oxide and nickel fluoride 1.0 Sodium silicate 2.5 Calcium oxide 2.0

This flux is remarkably effective in suppressing fuming of brass alloys used in brazing when heat is applied to them. Such brass alloys include common brasses such as the conventional copper zinc alloys and those referred to as nickel silver which include, in addition to the copper and zinc, from 8 to 2 0% nickel.

The compounds of boron oxide in the formulation of this invention include borates of potassium, sodium and lithium and also boric acid which can be substituted for any of the aforementioned alkali metal borates. The function of these borates is to serve as a vehicle for 3,175,933 Patented Mar. 30, 1365 dissolving or retaining in solution any of the metallic oxides formed in the elevated temperatures.

The alkali metal fluorides are a source of fluorine which ultimately reacts with the borates to form boron fluoride which is an active scouring agent that removes the surface oxide from the parent metal prior and during deposition. These fluorides together with calcium 0xide form a slag system having optimum viscosity characteristics whose fluidity maintains the flux molten and mobile at elevated temperatures even over extended periods of time.

The chloride salts also maintain the flux fluid and highly reactive prior to and during deposition.

The silicon-containing deoxidizers, which might also be provided by ferro-alloys of silicon such as ferrosilicon and silico-manganese, greatly help to suppress fuming and to increase the fluidity of the molten alloy.

An alkali metal hydroxide such as lithium hydroxide helps reduce the melting point of the flux since it itself has a low melting temperature, and it is highly subject to decomposition particularly when combined with reducing agents such as the aforementioned silicon hearing materials.

The fluoride and oxide of nickel or molybdenum combine readily with the oxides of graphite and carbides which are commonly present on the surface of cast iron parent materials. In addition they provide a source of nickel or molybdenum which greatly facilitates wetting and diffusion into the joint interface.

When this flux formulation is utilized with various brass alloys, the usual fuming of these alloys at elevated temperatures is remarkably suppressed. However the exact reason why the formulation of poisonous zinc oxide, of which fuming is a visible manifestation, is inhibited is not completely understood. This flux also tremendously aids the wetting ability of brass filler alloys on cast iron parent materials. The conventionally required rubbing of the alloy may therefore be eliminated, and considerable expense in brazing is also conserved because much less filler alloy than previously required may be utilized to create a strong bond. The thin flowing consistency of this flux also contributes to the valuable properties of this flux. Another advantage of this flux is its direct applicability upon dirty, oil-soaked or oxidized cast iron without any necessity for any prior cleaning. This is highly advantageous because cast iron under normal handling procedures in a foundry or fabricating shop is highly subject to surface contamination.

What is claimed is:

1. A flux for use in conjunction with a brass alloy consisting essentially of the following constituents in the indicated ranges of percentages by weight:

Constituent- A boron oxide compound selected from the group consisting of alkali metal borates and boric acid Alkali metal fluorides Alkali metal chlorides A silicon containing deoxidizer selected from the group consisting of silicon, ferro-silicon and silico-manganese Alkali metal hydroxide A mixture of from 10 to percent by weight of a member selected from the group consisting of nickel oxide and molybdenum 0xide with from 90 to 10 percent by weight of a member selected from the group consisting of molybdenum fluoride and nickel fluoride Alkali metal silicate and calcium oxide Range 3 4 2. A flux as set forth in claim 1 wherein said boron References Qited by the Examiner oxide compounds are alkali metal borates. UNITED SPDX-JFESv PA 3. A flux as set forth in claim 1 wherein said alkali metal y dmxi de is H thium hydroxide. 3,031,346 4/62 Wasserman et a1 14826 4. A flux as set forth in claim 1 wherein said alkali 5 DAVID RECKPrimWY Examine"- metal silicate is sodium silicate. WINSTON A. DOUGLAS, Examiner. 

1. A FLUX FOR USE IN CONJUNCTION WITH A BRASS ALLOY CONSISTING ESSENTIALLY OF THE FOLLOWING CONSTITUENTS IN THE INDICATED RANGES OF PERCENTAGES BY WEIGHT: CONSTITUENT- RANGE A BORN OXIDE COMPOUND SELECTED FROM THE GROUP CONSISTING OF ALKALI METAL BORATES AND BORIC ACID 35-82.7 ALKALI METAL FLUORIDES 6-33 ALKALI METAL CHLORIDES 8-32 A SILICON CONTAINING DEOXIDIZER SELECTED FROM THE GROUP CONSISTING OF SILICON, FERRO-SILICON AND SILICO-MANGANESE 0.5-4 ALKALI METAL HYDROXIDE 0.5-7.5 A MIXTURE OF FROM 10 TO 90 PERCENT BY WEIGHT OF A MEMBER SELECTED FROM THE GROUP CONSISTING OF NICKEL OXIDE AND MOLYBDENUM OXIDE WITH FROM 90 TO 10 PERCENT BY WEIGHT OF A MEMBER SELECTED FROM THE GROUP CONSISTING OF MOLYBDENUM FLUORIDE AND NICKEL FLUORIDE 0.3-14 ALKALI METAL SILICATE 1-10 AND CALCIUM OXIDE 1-8 